Purpose: To evaluate marginal fit as well as fracture resistance of zirconia implant abutment supporting two types of metal free CAD/CAM restorations. Materials and methods: Twenty ready-made ZrO 2 abutments resembling lower first premolar squeezed and stabled to its conforming titanium dummy implants were implanted in epoxy resin blocks. Samples were divided into two groups in relation to the material utilized for the fabrication of the copings; group (I) (n=10): zirconia copings, group (II) (n=10): breCAM.BioHPP copings. All copings were machined using CAD/CAM system. Samples were exposed to a fatigue procedure for 20,000 cycles. Marginal fit was determined using digital stereomicroscope. Fracture resistance was registered using universal testing machine. The samples were overloaded till last fracture occurred and load at fracture was documented. Analysis of data was examined using accessible software programme (SPSS 18). Results: BreCAM.BioHPP copings, group (II), registered a statistically significant higher mean vertical marginal gap value (122.08±25.05µm) in addition to higher mean failure load value (2828.47±735.4N) compared to zirconia copings, group (I) (27.06±3.2µm) (416.06±22.16N) respectively. Conclusions: Material type used for the fabrication of the copings influences marginal fit and fracture resistance. Zirconia coping samples showed higher marginal fit and lower fracture resistance than breCAM.BioHPP coping samples.With increasing number of patients who need highly esthetic restorations, tooth colored ceramic implant abutments have been introduced such as zirconia implant abutment, even after; it has been extensively protracted for clinical use (2) .

Purpose: Assess the effect of material selection as well as different fabrication techniques of metal ceramic (MC) and all ceramic crowns on their clinical outcomes, marginal and internal fit. Materials and methods: In vivo study(I); twenty-eight patients were provided with twenty-eight crowns restoring mandibular first molar tooth.Patients were distributed into 2 groups and 2 subgroups according to different materials and fabrication techniques: fourteen patients received MC crowns, group (I); seven patients received crowns with conventional casting of Co-Cr copings, subgroup (A) and seven patients received crowns with direct milling of Co-Cr copings, subgroup (B). Fourteen patients received IPS e.max press crowns, group (II); seven patients received crowns with conventional wax pattern, subgroup (A) and seven patients received crowns with 3D printing resin pattern, subgroup (B). The survival rate of these crowns was evaluated and statistically analyzed. In vitro study(II); one machined die was prepared to simulate crown preparation of mandibular first molar tooth. 60 crowns were constructed on die and divided into 2 groups (30 samples each) and 2 subgroups (15 samples each) according to different materials and fabrication techniques similar to in vivo study. Replica technique obtained to measure marginal and internal fit using Digital microscope. Results: The survival rate of MC and press crowns was 98% and 60% respectively. Press crowns and digital technique showed superior marginal and internal fit than MC crowns and conventional technique respectively. Conclusions: Material type and fabrication technique of MC and all ceramic crownsinfluence their clinical outcome, marginal and internal fit.

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Objectives: To compare the influence of vertical (featheredge) margin configuration versus horizontal (deep chamfer) margin configuration on fracture resistance of zirconia copings with the different occlusal thicknesses (0.5mm and 1mm). Materials and methods:Two stainless steel master dies were designed and then milled to mimic the coping preparation of the upper first premolar tooth and duplicated by means of epoxy resin to yield forty dies. 40 epoxy dies were distributed into two groups (n=20) in relation to the margin configuration types; feather edge (F) group (n=20) and deep chamfer (DC) group (n=20). Each group was subdivided into two subgroups (n = 10) concerning varied occlusal thickness (0.5 and 1 mm). Copings were fabricated from zirconia blank. For the testing of fracture resistance, a universal testing machine was used by subjecting the samples to a fixed load till failure occurred. Statistical analysis was then performed.Results: Feather edge margin with (1mm) occlusal thickness registered the highest mean fracture load (1117.81±124.90N) followed by deep chamfer margin with (1mm) occlusal thickness (1000.73±148.84N). While the feather edge margin with (0.5mm) occlusal thickness registered the lowest mean fracture load (282.31± 45.69N) with no significant difference between groups.Conclusions: Vertical margin configuration margin has a more promising fracture resistance than horizontal margin configuration, especially in (1mm) occlusal thickness. Although (0.5mm) restorations occlusal thickness exceeds the maximum chewing forces reported in the literature.